Patients with HFpEF suffer from exercise intolerance, increased risk for hospitalization and mortality, and poor QOL. Unlike patients with HFrEF, no drug or device therapies appear to be consistently beneficial in treating these problems. However, increasing evidence suggests that exercise training is effective for both partially reversing exercise intolerance and improving quality of life in these patients. Most such trials to date have been conducted in controlled research setting, versus integrating these patients in to a standard CR program. Also, since functional capacity is related to outcomes in these patients, exercise strategies aimed at further improving fitness are warranted. One such strategy is using higher intensity interval training (HIIT) in the CR setting, a strategy shown to be effective in patients with other types of CVD. This project is designed to test the feasibility of incorporating these patients into the CR setting, and training them using a methodology (i.e., HIIT) already shown to yield (in other patients with CVD) greater gains in fitness when compared to what was achieved using standard MCT alone.